In a large skillet over medium heat, cook turkey, onion, garlic and chili powder, breaking up turkey with spoon, until turkey is no longer pink, 8 to 10 minutes. Stir in tomato purée, beans, yellow pepper, and salt and pepper if desired. Bring to a boil, reduce heat to medium-low and simmer, stirring often, until thickened, 6 to 8 minutes.
Line a 13- x 9-inch (3 L) metal baking dish with foil; lightly oil foil. Layer tortilla chips and chili in pan; top with cheese. Watching carefully, broil about 8 inches from heat, until cheese is bubbly and chips are lightly toasted (about 1 minute). Top with green onion and cilantro. Serve with lime wedges for squeezing and low-fat sour cream for dipping, if desired.
Per serving: 460 calories, 14 g protein, 11 g fat (2 g saturated fat), 63 g carbohydrates, 9 g fibre, 64 mg cholesterol, 395 mg sodium